Thoughts in sleep perfect memory

Mon, 11/12/2012 -- Science News Desk

Sleep is beneficial to memory. A new study finds that sleep enhances consolidation of both gist and detail of experiences. So sleepless nights may not only wear you down, but may also leave your experiences less entrenched as memory.

Memory for a range of tasks is greater following an interval containing sleep relative to memory following an equivalent interval of wake. This benefit of sleep is thought to reflect the fact that memories are ‘replayed’ during sleep. The brain is known to be highly active during sleep and the neurons that are reactivated are the same as those that were active during recent waking experiences.

New research from the University of Massachusetts, Amherst, suggests an additional benefit of sleep in extracting the ‘gist’ of recent memories. In the study, Dr. Rebecca Spencer and her colleagues Shannon McKeon and Ed Pace-Schott had participants learn lists of related words (bowl, spoon, morning, breakfast, milk). Importantly, each list lacked a critical word which reflected the gist of the list (cereal). When recall of the lists was probed after sleep, participants were more likely to recall those critical words reflecting the gist of the list than they were if recall took place after wake.

The results are consistent with the neuroimaging studies that show that key components of the brain's emotional memory circuit activate more strongly during recall of previously learned emotional stimuli if sleep followed their initial encoding.

The study was published last week in the peer-reviewed journal PLOS ONE.

An important aspect of this study was the manipulation of the emotion of the words. Emotional memories are thought to be strong, reflecting their salience and future relevance. Yet, nonetheless, this study found that false memories (recall of never-presented critical words, i.e., the gist) was just as prominent when word lists were emotionally negative (slaughter, execute, shoot, etc) as when they were neutral. These results support the adaptive function of sleep in both remembering and in extracting memory details.